This week, these ten stocks have the worst year-to-date performance. Each of these also rates an “F” (“strong sell”) on Portfolio Grader.

Since the first of the year, Gerdau S.A. Sponsored ADR Pfd (GGB) has dipped 44.4%. Gerdau is a Brazilian corporation that produces crude steel and related products. For more information, get Portfolio Grader’s complete analysis of GGB stock.

Since the first of the year, Helix Energy Solutions Group, Inc. (HLX) has dipped 47.7%. Helix Energy Solutions is a marine contractor and operator of offshore oil and gas properties and production facilities. Shares of the stock are being traded at a very rapid pace, up 122.9% from the week prior. For more information, get Portfolio Grader’s complete analysis of HLX stock.

Shares of AIXTRON SE Sponsored ADR (AIXG) have sunk 48.7% since the first of the year. Aixtron provides deposition equipment, such as that used in lighting, fiber optic communication systems, and mobile telephone applications, to the semiconductor industry. For more information, get Portfolio Grader’s complete analysis of AIXG stock.

Since January 1, Stone Energy Corporation (SGY) has plunged 48.9%. Stone Energy is an independent oil and natural gas company engaged in the acquisition, exploration, exploitation, development and operation of oil and gas properties. As of July 23, 2015, 15.4% of outstanding Stone Energy Corporation shares were held short. For more information, get Portfolio Grader’s complete analysis of SGY stock.

Shares of 3D Systems Corporation (DDD) have slumped 50.2% since the first of the year. 3D Systems engages in the design, development, manufacture, marketing, and servicing of 3D printers and related products, print materials, and services. As of July 23, 2015, 32.7% of outstanding 3D Systems Corporation shares were held short. For more information, get Portfolio Grader’s complete analysis of DDD stock.

Since January 1, Ocwen Financial Corporation (OCN) has fallen 53.4%. Ocwen Financial is a diversified financial services holding company. As of July 23, 2015, 24.5% of outstanding Ocwen Financial Corporation shares were held short. Trade volume is up 98.4% from the previous week. For more information, get Portfolio Grader’s complete analysis of OCN stock.

Shares of Cliffs Natural Resources (CLF) have slumped 55.2% since the first of the year. Cliffs Natural Resources is an international mining and natural resources company. As of July 23, 2015, 39.9% of outstanding Cliffs Natural Resources shares were held short. Shares of the stock have been changing hands at an unusually rapid pace, up 222.4% from the week prior. For more information, get Portfolio Grader’s complete analysis of CLF stock.

Since the first of the year, Magnum Hunter Resources Corporation (MHR) has tumbled 66.7%. Magnum Hunter Resources explores for oil and natural gas. As of July 23, 2015, 26.7% of outstanding Magnum Hunter Resources Corporation shares were held short. For more information, get Portfolio Grader’s complete analysis of MHR stock.

Shares of Natural Resource Partners (NRP) have dipped 73% since the first of the year. Natural Resource Partners owns and manages coal properties in Appalachia, the Illinois Basin, and the Western United States. For more information, get Portfolio Grader’s complete analysis of NRP stock.

Since the first of the year, Peabody Energy Corporation (BTU) has dipped 84.9%. Peabody Energy mines steal, coal, and metallurgical coal to sell to electric utilities and industrial customers. As of July 23, 2015, 35.5% of outstanding Peabody Energy Corporation shares were held short. For more information, get Portfolio Grader’s complete analysis of BTU stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.